Three Phase Electricity

[--GQ--]

Re: Three Phase Electricity

OOOOh boy. Some of you are relying too heavily on Google. Wrong Wrong Wrong!!!

 

[WardenJ]

Re: Three Phase Electricity

OK, so if it's all wrong, could you shed some light on what is correct?

 

[--GQ--]

Re: Three Phase Electricity

Warden not all of it. Some. Check the archives. There should be several posts relating to Single phase and 3 phase power I posted awhile back.

 

[tommays]

Re: Three Phase Electricity

The ship has 115, 220, 480 and 600 in these configurations:<br /><br /> * 1-600VAC 250amp 3 phase 60hz (provided from SS Buss or Propulsion buss)<br /> * 1-480VAC 225amp 3 phase 60hz (provided from SS Buss or Propulsion buss)<br /> * 2-480VAC 80amp 3 phase 60hz (from SS buss)<br /> * 2-480VAC 30amp 3 phase 60hz (from SS buss)<br /> * 2-220VAC 30amp 2 phase (from SS buss) – **No such thing as 220 – 3 phase on this vessel**<br /> * 2-115vac 30amp 3 phase (from Clean power buss)<br /><br /><br />Warren<br /><br />I have looked around and from what i see very littel of whats correct on LAND is correct on a ship so i would keep that in mind <br /><br />Here is some info that seems to cover what your trying to do<br /><br /> http://www.marcspages.co.uk/pq/7140.htm <br /><br /> http://www.mikeholt.com/codeForum/index.php <br /><br />tommays

 

[--GQ--]

Re: Three Phase Electricity

Warden if you can't find it, here is a quick view. Diagrams below may also help.<br /><br />There are two types of power commercially available for the general public. In fact they are used thru-out the world. They are Single and 3 Phase system.<br /><br />In a single phase system, power is derived from a single phase transformer. A 240v winding on the secondary side with two ends commonly referred to as side "A" and "B". A center neutral tap splits the winding into two sections. Voltage from either side "A" or "B" to neutral is 120v. Voltage across the two sides is 240. <br /><br />Often Single Phase power is confused as "Two Phase" because of the "A" and "B" side. Although not important, it is not correct. The word "single" in-conjunction with the word "phase" is used to describe a type of electrical power generation produced by a single winding generator set thus having zero degree of electrical separation "Two Phase" implies there are two windings. See diagram 1. Another example below may also help. <br /><br />A typical 24v power set-up in a boat has two batteries connected in series. Voltage from the center to either side of the batteries is 12v. Voltage across both batteries is 24v. See diagram 2. Before someone say, "But this is DC power", the principle is the same as single phase power.<br /><br />A three Phase power set-up is a bit more complex. In a three phase generator, three windings are present. Each physically separated 120 degrees apart thus producing three single phase sine waves electrically 120 degrees apart. Hint: the term "three phase". Two typical set-ups are Wye and delta configuration. Each set-up has two subcategories. Series Wye, parallel Wye, Series Delta and Parallel Delta. For simplicity, let us use the most common Wye as an example. This particular configuration has 3 or 4 wires. To achieve dual voltages capability, the 4th wire (neutral) must be used. The other three designated as "A", "B", "C". Better known, Phase A, Phase B, Phase C. See diagram 4<br /><br /><br />

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[WardenJ]

Re: Three Phase Electricity

GQ-<br /><br />Thanks for the diagrams. I am pretty sure I get the concepts that you are describing. I'm assuming when you say "Neutral" you mean a current carrying conductor bonded with Earth.<br /><br />On the boat, it doesnt look like we have an earth-bonded neutral and dual voltages are achieved through transformers. If it is correct that a single voltage three phase system does not require such a neutral, then I am fairly confident this is how the 110 system is derived on our ship. My 110 panel has three incoming leads, if I measure across any two I get 110, and measuring any one to the hull (ground), produces something along the lines of 75-80. This seems to mimic a three phase system fairly well, and it wouldnt require a neutral bonded to earth (through the hull) if the above assumption is correct (that single voltage three phase doesnt require an earth bonded neutral). <br /><br />What I was saying before was that if this is the case, then it wouldnt be correct to just take one of the 440 leads and the hull to make 260 volts or whatever for the galley range, because based on the way the rest of the boat is wired, I'm not supposed to be using the hull for anything. I'd need another transformer. Then I could just take two of the lines coming out of there, (making 240V) and wire up the range, but the range still wants a neutral wire based on the installation instructions, and there would be the issue of where to put that (since it cant go to the hull).

 

[SS MAYFLOAT]

Re: Three Phase Electricity

GQ's diagrams are excellent. I talked to our electrician. His opinion was that marine applications are more stringent and complicated than shore power. He recommended calling Square D and ask their engineers in the transformer department. There they will know what you have and what to do to meet your needs. <br /><br />Be careful not to wire something up and become the next Philadelphia Experiment!<br /><br />

 

[WardenJ]

Re: Three Phase Electricity

Hey thanks SS. They were very helpful and told me exactly what I needed. A 480V in, 240/120V out transformer. It will give me the two 240 lines and the neutral line for the 120 that the new range requires, with no connection to the hull or anything.

 

[SS MAYFLOAT]

Re: Three Phase Electricity

WJ, just make sure you get the right size/capacity. Almost like a generator, it is only good as the load it can pull. What about an outlet for a cloths dryer? It is actually a smaller load than that of your stove/oven. BTW, yer welcome. I had to go through them when I went from 240 open delta to 208 3 phase. Hope you don't have a problem with a weight limit, they do get a bit heavy.

 

[WardenJ]

Re: Three Phase Electricity

Well according to Square D and the amp rating of the range, a 10 kVA transformer will do the trick. They have one that isnt too large which should go nicely somewhere in the Engine Room, and it only costs twice what we paid for the range...<br /><br />This will be the only 240 service anywhere on the boat, so there is no clothes dryer plug to pull from (if that is what you meant). Hmm, I wonder if we can pull off of it for a plug for our welder...for when we arent cooking...now the wheels are turning